1. Field of the Invention:
This invention relates to polyisocyanurate resins. More particularly, it relates to high-density polyisocyanurate resins having improved properties such as rigidity, high-temperature properties, impact resistance and curing characteristics, and a process of making the same.
2. Description of the Prior Art:
It has been known that polyisocyanurate foams have good heat resistance and flame resistance. It has also been proposed to produce such polyisocyanurate foams with heat-resistant heterocyclic structures formed by cyclization of grafted side-chain acrylonitrile groups, using polymer polyols (acrylonitrile-grafted polyetherpolyols). However these foams are high-expanded, and brittle and not high-impact, and their heat resistance and rigidity are not fully satisfied.